Understanding Mitosis Phases

Mitosis and Cytokinesis

Mitosis

Mitosis (discovered by botanist Eduard Strasburger) is a process of nuclear division exclusive to eukaryotes, ensuring the segregation and equal distribution of sister chromatids between the daughter cells during cell division.

Mitosis is an equational division that ensures the conservation of the genetic and chromosomal makeup of the species. Thus, mitosis of a parent cell yields two daughter cells with the same number of chromosomes and genetic information as the parent cell.

Mitosis can be structured into five phases: prophase, prometaphase, metaphase, anaphase, and telophase.

Prophase

During prophase, the following key changes occur:

• Chromatin Condensation: Chromatin condenses into visible chromosomes, each composed of two sister chromatids joined at the centromere. These are called dyads. Kinetochores are organized at the centromeres.
• Nucleolus Disappearance: The nucleolus disappears as chromosomes condense.
• Mitotic Spindle Formation: The mitotic spindle begins to form.
  • In animal cells, centrosomes migrate to opposite poles, organizing microtubules into the mitotic spindle (astral).
  • In plant cells (lacking centrosomes), the anastral spindle forms from cytoplasmic microtubule organizing centers (MTOCs).

Microtubules organized from the centrosomes in animal cells are typically of two types:

• Polar microtubules: Extend from poles towards the equator, overlapping with those from the opposite pole.
• Astral microtubules: Radiate from centrosomes towards the cell periphery.